Remote signal system



Aug. 4, 1970 E. w. STREIT REMOTE SIGNAL sYsTEM 2 Sheets-Sheet 1 FiledNOV. l5, 1967 Aug. 4, 1970 E. w.s1-RE|T 3,523,162

REMOTE SIGNAL SYSTEM Filed Nov. 13, 1967 2 Sheets-Sheet 2 .es mm g *no W\.oQ

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2A/fe /1/ @ref/r WM@ @gg/fg@ United States Patent O1 hcc 3,523,162Patented Aug. 4, 1970 3,523,162 REMOTE SIGNAL SYSTEM Elmer W. Streit,4152 N. Whipple St., Chicago, Ill. 60618 Filed Nov. 13, 1967, Ser. No.681,992 Int. Cl. H04m 1]/04 U.S. Cl. 179--5 10 Claims ABSTRACT OF THEDISCLOSURE A remote alarm system employing telephone lines tointerconnect a central station, such as a police station, with a numberof remote stations, such as stores, banks, etc., and a central stationalarm detecting and signaling circuit are disclosed. The alarm systemhas special provisions against false actuation of alarm signals bytemporary short or open circuiting of the phone lines and yet providesfor identification of and distinction between a long term short or opencircuit and a true alarm signal. The circuit also provides means foridentifying a new alarm situation from existing but uncorrected alarmsituations.

BACKGROUND OF THE INVENTION The present invention is directed toward anew and improved remote alarm system and circuit of the type used tonotify a central station of an alarm condition at one or more of aplurality of remote stations. A particular preferred application of thepresent invention is found in notifying a police station of an alarmcondition, such as the breaking of a burglar alarm circuit, at a distantbank or store. While this application is the currently envisioned bestmode of practicing the invention, it will be readily appreciated bythose skilled in the art of remote alarm systems that many otherapplications of the principles taught herein can be made.

Many systems and circuits have been proposed in the past foraccomplishing the task of alerting a central station of conditions atone or more remote stations. One such suggestion is shown in the U.S.Pat. No. 3,254,334 entitled Electrical Protection System -UtilizingReverse Polarity Line Testing With Unidirectional Current Devices HavingReverse Breakdown Characteristic, which issued on May 31, 1966, in thename of L. H. Mitchell.

Similar systems are taught in the U.S. Pat. No. 2,944,252 entitledIntruder Alarm System, which issued on July 5, 1960 in the name of M. W.Muehter, and in the U.S. Pat. No. 3,069,673, entitled RemotelyControlled Alarm System, which issued on Dec. 18, 1962 in the names ofE. I. Ward et al. l

While these and other prior art systems and circuits may functionadequately for some purposes and in some environments of use, theygenerally have one or more disadvantages such as requiring excessiveinstallation time, requiring specially trained attendants, being undulycomplex and therefore subject to frequent breakdown, providing an alarmindication at the central station only in response to a special signal,thus allowing the system to be defeated by cutting the communicationline between the remote and central stations, making no distinctionbetween an alarm signal and communication line trouble, or respondingtoo readily to temporary breaks or shorts in the communication line.

The present invention has as its object the overcoming of the aforesaiddisadvantages, in a novel system that is both economic and easy toinstall and operate.

In accordance with the present invention direct current power and alarmactivating mechanism for operating a remote station units trouble andalarm signal generation is located at the local station. Interonnectingof the units with the central station is preferably via rented or leasedpublic service company private telephone line facilities.

The use of public service company facilities presents a greaterpossibility of a false trouble alarm, due to the fact that thefacilities are exposed to the elements. More often than not, theseconditions are of a momentary nature, but nevertheless when they doactivate they may actuate a signal at the central station so that adisposition must be made. It is desirable to reduce the number of thesefalse signals as long as security is not jeopardized. It is one of thefeatures and advantages of this invention that this is accomplished inan eflicient and effective manner.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the present inventionwhich are believed to 'be novel are set forth with particularity in theappended claims. The invention, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription taken in connection with the accompanying drawings, in theseveral figures of which like reference numerals identify like elements,and in which:

FIG. 1 is partly schematic and partially block diagram of the overallremote signal system of the present invention;

FIG. 2 is a schematic circuit diagram illustrating one possibleembodiment for the remote signal unit of the remote stations of FIG. l;and

FIG. 3 is a schematic circuit diagram of the alarm unit of the centralstation of the system of FIG. l.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. l thedepicted system is generally designated by the number 10 and includes aplurality of remote or local stations 11, individually designated 11A,11B, 11C and 11N, each connected to a single central station 12 via acommunications telephone line 13A, 13B, 13C and 13N. As indicated, theremay be an indefinite number of remote stations 11 each interconnected byits own line 13 to the central station 12. While in theory the centralstation 12 may accommodate an unlimited number of remote stations 11,experience has found that the dictates of practical considerations limitthe number of remote stations 11 that a single central station unit mayaccommodate to a number of the order of one hundred.

As preferably practiced the invention system 10 employs remote or localunits at stores, banks, or other establishments whose management desiresprotection, with the central unit at a regional police station. Thus,the remote units are responsive to the actuation of a burglar or robberyalarm sensor or other device.

Of course, the invention may be adapted to other functions, such as realarm or'security within a large plant. However for definitiveness ofdisclosure it will be here described in conjunction with its presentlycontemplated best mode of operating, as a burglar or robbery alarmsystem for alerting a police station located at a distance from theprotected establishments.

The remote stations 11 are thus each located in a differentestablishment which is remotely located from the police station 12. Eachremote station 11 comprises, as in station 11A depicted in FIG. 1, analarm sensor 14 and a power supply 15 coupled to an alarm signalgenerator 16. The alarm sensor 14 may be any connectional device such asthe conventional foil circuits used on many store windows, a manuallyoperated foot button alarm such as often used in bank cages or any otherdevice that senses or is actuated in response to an alarm situation.

The lines 13 interconnecting the remote stations 11 and the central orpolice station 12 are preferably telephone lines leased from the localtelephone utility company. While other lines may be employed, theleasing of private lines from the telephone company has the twinadvantages of being economical and easy to accomplish. Thus, a new storelmay be readily added to those subscribing to the service of the systemwith a minimum of bother and effort on the part of the subscriber or thecentral station operator. Beside the convenience and economy of theleased telephone lines they are often the only practical method ofobtaining intercommunication between a large number of widely separated,often by many miles, establishments and a central station.

However, the use of leased telephone lines while very advantageous formost purposes does result in magnification of the problems found withany remote alarm system. The problem of protection against falseactuation that can result from temporary shorts or groundings or openson the communication lines is thus accentuated. One of the majoradvantages of the present invention is the minimization of this problem.

At the central station 12 each line 13 is connected to an individualmodule 17. That is line 13A is connected to module 17A, line 13B tomodule 17B, line 13C to module 17C and line 13N to module 17N. Each ofthese modules 17 has visual alarm indicators comprising an indicatingmeter dial 18 and a pair of lights 19 and 20. While the light 19 ispreferably red and the light 20 is preferably yellow, any convenientdifferentiating coloration could, of course, be used. In addition, asubscribed indicia such as the name plates 21 are also mounted on eachmodule 17 to aid the attendant (normally the police desk sergeant in apolice station installation) in identifying the source of the alarm.Each of the modules 17 are preferably mounted in a panel displaypositioned facing the attendant.

The modules 17 are each coupled via one of the lines 22A-22N, to acommon bus bar or line 23 which is connected to an audio alarm unit 24.The unit 24 preferably sounds an audio alarm of a dissonant type, suchas a buzzer, to call the attendant.

A remotely located silencer 25 for silencing the audio alarm 24 isprovided connected via a bus bar 26 to individual ones of the modules17A-17N. The silencer 25 is preferably a simple push button switch andis preferably located nearby the attendant to minimize any annoyance tohim that may result from the continued sounding of the audio alarm afterit has complied its notifying task. The unit 12 also includes aconventional power supply 28 connected via a bus bar 29 to each of themodules 17 and also connected to the silencer 25 and the audio alarm 24.

One operable design for the alarm signal generator 16 of the remotestations 11 is depicted in detail in FIG. 2. Referring to that gure, thetwo conventional conductors of the telephone line 13 are theredesignated 13 and 13 and are connected to switch means of the relaytype. The lines 13 and 13 are respectively connected to the switchblades of a pair of ganged relay switches 30 and 31. The switches 30 and31 are each of the two contact type and are mechanically biased so as tonormally make contact between their blades and a first contact 32 or 33.The contact 32 is connected via line 34 to the second or normally opencontact 35 of the other switch 31. This contact 35, and thus contact 32via line 34, are connected via a conductor 36 to the negative terminalof the voltage supply 15. The positive terminal of the supply 15 isconnected via a closed switch 37 and a line 37 to the second or normallyopen contact 38 of switch 30 and also, via line 39, to contact 33 ofswitch 31. The switch 37 may be eliminated without effecting theoperation of the basic circuit, as it functions to allow employment ofan optional alarm subsystem 5 that will be discussed below.

Y 36 to the negative side of supply 15 while the line 13 is connected toits positive side via the blade of switch 31, contact 33 and lines 39and 37. When the ganged switch blades of switches 30 and 31 are thrownthe polarity is reversed. That is, the line 13 is connected to thepositive terminal of supply 15 via the blade of switch 30, contact point38 and line 37, while the line 13 is connected to the negative terminalof source 15 via contact 35 and line 36.

This reversal of polarity constitutes the alarm signal and is achievedby the actuation of the relay coil 40 which is connected across thesensor 14. The sensor` 14 supplies a current through the coil 40 inresponse to its sensing of an alarm condition. This results in aswitching of the blades of the switches 30 and 31 and causes thepolarity of the voltage across lines 13 and 13" of the telephone line 13to be reversed.

Referring to FIG. 3, the circuitry of the modules 17 and itsinterrelation with the audio alarm unit 24, the silencer `25 and thepower supply 28 will now be described. The inputs from the phone lineare designated 13' and 13 in conformity with FIG. 2. Thus, the line 13is normally negative and line 13 is normally positive with the polarityof the lines beingreversed whenever a true alarm condition exists. Theline 13' is connected to an input terminal 41 lwhile line 13 isconnected to an input terminal 42.

An ammeter 43, whose meter dial 18 is depicted in FIG. 1, is connectedbetween the terminal 41 and the junction 44 of a pair of seriesconnected diodes 45 and 46. The diode 45 is connected so as to allowconventional current ow essentially only into the junction 44 whilediode 46 is connected so as to allow conventional current ow essentiallyonly out of the junction 44. The other side of the diode 46 away fromthe junction 44 is connected to one end of a relay coil 47. The otherend of the coil 47 is connected to a junction 48 with a line 49connected thereto and to the terminal 42.

Also connected to the junction 48 is one end of a second relay coil 50,the other end of which is connected to the diode 45. `Connected acrossthe coil 50 between the junction 48 and the junction 51 between the coil50 and the diode 45 is a capacitor 52.

The relay coil 47 functions to move a switch blade 53. The blade 53 hasa single contact point 54 associated with it and is mechanically biasedas to have the switch formed thereby normally open in the absence ofenergization of the coil 47.

The relay coil 50 functions to move a switch blade 54 which ismechanically biased so as to normally make contact `with a contact point55 in the absence of energization of the coil 50. The switch blade 54 iselectrically connected to the switch blade 53 by a conductor 56 which isalso connected to a line 57.

The line 57 is connected to the positive terminal of the power supply ordirect current voltage source 28 through a terminal 58. The terminal 58is connected to a common bus bar 59 which may have many of the modules17 connected thereto. The negative terminal of the voltage source 28 isconnected to a similar bus bar 60 to which the terminals 61 of themodules 17 are connected in common. For purposes of analysis thepotential of bus bar 60, terminal 61 and a conductor 62 connectedthereto shall be taken as a reference of termed ground potential, itbeing understood however that this potential level may not be connectedto ground and may be at a different relative level from the referencepotentials of other parts of the system.

The relay Contact point 53 of the relay formed by that contact point,the coil 47, and the blade 53 is connected via a conductor 63 to thejunction 64 between two series connected diodes 65 and 66. The diodes 65and 66 are each connected so as to allow conventional current flowessentially only away from the junction 64.

The other side of diode 66 away from the junction 64 is connectedthrough a resistance 67 to one side of the lamp 19, the other side ofwhich is connected to the line 62. The other side of diode 65 away fromthe junction 64 is connected via a line 68 to the contact point 55.

The module 17 also includes two relays generally indicated by 69 and 70each of which has a plurality of ganged switch blades operated by therelay coil. The relay 69 comprises a ganged first and second switchblade 71 and 72 moved by a relay coil 73. The relay 70 comprises afirst, a second, a third and a fourth ganged switch blades, respectivelydesignated 74, 75, 76 and 77 and all controlled by a relay coil 78. Theblades 71, 74, 75, 76 and 77 each have only a single contact pointdesignated, respectively, 79, 80, 81, `82 and 83 associated `with them,while the blade 72 is part of a make before break switch which includesa first contact point 84 which is itself a switch blade for a secondcontact point 85. The blade 72 is mechanically biased to be open, absentenergization of the coil 73, with respect to point 84 while the contactpoint 84 is mechanically biased to be closed against the point 85 sothat the contact between points 85 and 84 is normally closed.

The point 84 of relay 69 is connected via a line 86 to line 68. Thecontact point 85 is connected via a line 87 to one side of the relaycoil 78. The blade 72 is connected via line 88 to one side of the relaycoil 73. The other sides of both these coils 73 and 78 are joinedtogether and connected via a bus bar 89 to reference potential source,line 60.

The other switch blade 71 of relay 69 is connected via a line 90 to thecontact 80 of blade 70 while its contact point 79 is coupled through aresistor 91 to the positive potential line 57. The conductor 90 isconnected through a resistance 92 to one side of the lamp 20, the otherside of which is connected to reference potential line 62.

The first, second, and third switch blades 74, 75 and 76 of relay 70 areall connected in common via a conductor 93 to the positive potentialline 57. The contact point 81 of blade 75 is connected to an outputterminal 94 which is, in turn, connected to a bus bar 95. The bus bar 95is further connected to one side of the audio alarm unit 24 which isalso connected via a conductor 96 to the negative bus bar 60. Each ofthe modules 17 have an output terminal 94 which are connected in commonto bus bar 95. The contact point of blade 76 is connected via line 97 toline 86.

The blade 77 is connected via a line 98 toy module output terminal 99which is connected in common with the similar outputs of module 17 to abus bar 100. The bus bar 100 is connected to one terminal of a pushbutton switch of the silencer 25. The other terminal of the push buttonswitch of silencer is connected via a line 101 to positive bus bar 59.The point 83 associated with blade 77 is connected via a line 102 to thejunction of line 88 and coil 73.

Having described the overall circuit of FIG. 3, its operation will nowbe considered. When there is no alarm condition present at the remotestation connected by the leased telephone line 13 to the module inputterminals 41 and 42, and when there is no abnormal interference with theservice of the line 13, the conductor 13" will be positive with respectto conductor 13 and a small current will ow between the lines 13 and 13through the terminal 42, the line 49, the relay coil 50, the diode 45and the ammeter 43 to the terminal 41. Furthermore, a charge will havebeen built up across capacitor 52 and current fiow through the coil 47is prevented by the diode 46. The current flow through the coil 50maintains the normally closed relay switch of blade 54 and blade contact55 open and the lack of current through coil 47 keeps the normally openrelay switch of point 53 and blade 53 open. As such, the module 17 drawsno power from CII the supply 28 and the visual indicators, save formeter dial 18, are not actuated.

When an alarm signal is sent by the remote station the polarities ofconductors 13 and 13" are reversed. The reversal of polarities cause acurrent to flow from terminal 41 through the meter 43, in the oppositedirection, through the diode 46, the coil 47, the line 49 and theterminal 42. This current operates the relay switch blade 53 to causedirect current to ow from the source 28 through the bus bar 59, theinput terminal 58, the line 57, the line 56, the blade 53, the contactpoint 53', the line 63, the junction 64, the diode 66, the resistance67, the lamp 19, the line 62, the terminal 61 and the bus bar 60. Thiscurrent lights the red alarm lamp 19.

A current is also caused to immediately fiow through a closed currentpath from the positive line 57 to the negative line 62 through thejunction point 64, the diode 65, ythe line 68, the line 86, the movablecontact point 84, the fixed contact point 85, the line 87, the coil 78and the bus 89. This current causes, after a momentary delay, the gangedfirst, second, third and fourth relay switches of blades 74-77 to close.This in turn causes current to flow from positive line 57 through line93, the first closed switch of blade 74 and contact 80, line 90,resistance 92 and the trouble lamp 20, to the line 62, thereby lightingthe lamp 20.

At the same time, current is caused to ow from line 93 through thesecond relay switch of blade 75 and `blade contact 81, output terminal94, bus bar 95, through audio alarm unit 24, the line 96 to the negativebus bar 60 thereby sounding the audio alarm.

The direct current potential present on line 93 is also simultaneouslyapplied through the third relay switch made up of blade 76 and bladecontact 82, to the line 97 and from thence to line 86. This serves as asecond current path to the switch of blade 53 and contact 54.

An additional current path to line 86 results from the de-energizationof coil 50. Upon the reversal of polarity current can no longer flowthrough the diode 45. However, the capacitor 52, in accordance with animportant feature of the present invention, provides a transcendentcurrent path through the coil 50 for a short period after the potentialreversal. Eventually, the current through the coil 50 drops below thelevel necessary for maintaining the switch of blade 54 and contact 55open and that switch is closed. This provides an additional current paththrough the blade 54 and the contact point 55 to the line 68.

The first relay switch, made up of switch blade 74 and blade contact 80,also serves to connect the positive potential of line 93 therethrough toline 90 and switch blade 71 of the first relay switch of relay 69.

The fourth switch of relay electrically connects the push buttonsilencer 25, via the line 100, the terminal 99, the line 98, the closedfourth relay switch, and the line 102 to one end of coil 73. No currentflows through this path as the push button switch 25 open-circuits thecurrent path between the positive bus bar 59 and the negative bus bar 89and line 62.

Thus, when an alarm signal reversal of polarities occurs on conductors13 and 13 the module 17 causes the lights 19 and 20 to light, and theaudio alarm unit 24 to sound. The ammeter 43 also indicates a currentfiow in the opposite direction than before and thus provides anothervisual indicator of the alarm situation existing at the remote station.

The audio alarm 4will continue to sound until the push button silencer101 is depressed by the attendant. Therefore, if the alarm signal isreceived during the temporary absence of the attendant, the alarm willcontinue to sound until his return.

The audio signal is silenced by the making or closing the circuit pathfrom the positive bus bar, through the line 101, the push button switchsilencer 25, the line 100, the module terminal 99, the line 98, theblade 77, the blade contact 83, the coil 73 and the line 89 to negativeline 62. This results in a flow of current through relay coil 73 and theconsequential movement of the ganged Switch blades 71 and 72.

The movement of blade 72 into contact with blade contact 84 closes asecond current path for coil 73. This path, from positively connectedline 86 (through relay switch blades 53 and 54) the blade contact 84,the blade 72, the line 88, through the coil 73, to negatively connectedbus bar 89, maintains relay coil 73 energized even though the pushbutton switch of silencer 25 is returned to its open circuit condition.As the blade 72 is further advanced, it moves the movable contact 84 outof contact with the contact point 85. This causes the open circuiting ofthe current path through relay coil 78 which results in the opening ofthe four switches of relay 70. The opening of the fourth switch made upof blade 77 and blade contact 83 open circuits the current path from thesilencer 25 and assures that further depressions of the push button willhave no effect on the circuitry of the module 17.

The opening of the third switch of relay 70 prevents current flowthrough line 97 to the line 86. The opening of the second relay switchopen circuits the current path to the audio alarm unit 24 and silencesthe audio alarm.

The opening of the first switch of relay 70 prevents current flowthrough the line 90 and would result in the extinguishing of the lampsave for the alternate current path formed by the closing of the firstswitch of relay 69. This path, from positive line 57 through resistor91, the blade contact 79, the blade 71 to the line 90, is closedmomentarily before the opening of circuit through the first switch ofrelay 70, causing no extinguishing of the lamp 20. However, because ofthe resistor 91 the lamp 20 is caused to glow with reduced brightness.This allows for easy differentiation by an attendant between modules 17.If this light were not dimmed it would be difficult for an attendant todistinguish between it and a subsequent alarm indicating module 17.

Should the alarm signal from the remote station now be replaced by thenormal signal, that is the polarities of conductor 13' and 13" wouldrespectively be returned to positive and negative again, the relayswitches formed of blades 53 and 54 and their associated contacts 53 and55 would be opened. This would cause lamp 19 to be extinguished, therelay switches of relay 69 to open (reclosing the contact between makebefore break contact 84 and contact 85) and extinguishing the lamp 20.This would restore the module to its normal condition, in

which it is ready to receive another alarm signal and to repeat theabove described operation.

Should the alarm signal have been received at the terminals 41 and 42but normal condition restored before the pushing of the push buttonsilencer by the attendant, the module 17 -would not be restored tonormal. This is an advantage of the inventive circuit, in that itprevents restoration to normal by, for example, a burglars resetting thesignal generator 16 at the remote station 11.

Other conditions that the module 17 may indicate are a short or opencircuit on the telephone line 13. In either of these cases no currentwill flow between the terminals 41 and 42. Should the condition be atemporary one, such as occasioned by a telephone repairman temporarilycutting into the line 13 in a search for another line, no signal willresult. This desirable feature of the present invention is provided bythe capacitor 52 which stores a sufficient charge to maintain a currentthrough the coil 50 for a short period after the cessation of thecurrent between the terminals 41 and 42. In practice, approximately twoseconds is considered to be the proper period of delay and thecapacitance of the capacitor 52 is chosen accordingly.

lf the short or open circuit between the conductors 13', 13 continuesbeyond the delay period, the current in coil will fall below the levelnecessary to keep open the normally closed relay switch formed by blade54 and blade contact 55 and that switch will close. This closureactuates, in the aforesaid manner, the audio alarm 24 and the troublelamp 20. The alarm lamp 19 is not actuated by the short or open circuit.The audio alarm may be silenced only by operation of silencer 25 by thecentral station attendant. The trouble lamp will remain lighted at areduced level of illumination thereafter while the short or open circuitcontinues. Should conditions be restored to normal the light 20 will beextinguished.

As mentioned before the use of telephone lines presents a greaterpossibility of a false trouble alarm, due to the fact that thefacilities are more exposed to the elements. More often than not, theseconditions are of a momentary nature, but nevertheless when they doactivate the module 17, a disposition must be made by the attendant. Itis desirable to reduce the number of these false signals as long assecurity is not jeopardized. The capacitor 52 provides a momentary delayof, e.g., one to two seconds before the operation of the trouble relayswitch 54-55. Security is not jeopardized for an alarm type signal,since the action of the alarm relay 54, 54', and rectifierinstantaneously initiates an alarm signal.

If a signal is once initiated, it is locked-in to permit definiteidentification and disposition of it. Uncertainty would result with anon-locking unit if normal conditions were restored between perceptionof the audible signal and attempted identification of the visual signal.Uncertainty would lead to laxity on the part of the central stationattendants and jeopardy of security.

The circuit of FIG. 3 accomplishes this locking-in by means of the relay70. The lock-in feature is cut out only after the silencer push buttonswitch 25 is manually operated. In the interim, definite identificationmay be made. If normal conditions were restored in the interim, the unitwould automatically restore itself upon the pressing of the push button25.

The above described circuit is also designed so that only a single pushbutton switch 25 is required to silence the audible signal originatingfrom any unit. This feature is important in communication centers suchas a metropolitan police district headquarters. It is accomplished bymeans of the make before break contacts 72, 84 and 85 of relay 69 andthe make contacts 77 and 83 of relay '70. It permits locating of thelarger space requiring module cabinets away from the attendant so thatmore frequently used telephone switchboard and radio transmittingequipment may be conveniently placed for attendants. The single pushbutton also provides for more efficient operation by handicappedpersonnel.

The circuit also provides for differentiating between a previouslyreceived and a newly received signal. A previously received signaltrouble lamp 20` will have been dimmed due to the fixed resistor 91while a newly received signal trouble lamp will be bright.

An alarm type signal is initiated by reversing the direct currentpolarity to the transmission conductors at the local or remote station.Since the recti-fiers 65 and 66 are associated primarily with this alarmtype signal, a discussion of their importance follows.

If the alarm relay and associated alarm lamp circuit were eliminated,and the winding of the relay were replaced by an equivalent valueresistor, an alarm type signal could still be received by observing thezero center reading meter. Two objections to this type of indicationwould be that the more discernible alarm lamp signal and theinstantaneous alarm signal feature would be eliminated. Theinstantaneous alarm feature could be incorporated in this type circuitby removing the capacitor, but this would revert the system to increasedfalse alarm possibilities previously mentioned.

If the alarm relay circuitry would be as shown, but with rectifier 66shortcd and rectifier 65 removed, an

alarm type signal would be received much in the same manner as mentionedabove. This type circuit would, however, have the advantage of the morediscernible lighting of the lamp 19, but the problem of the delayedaudible signal or increased false alarms would still exist.

If the alarm relay circuitry would be as shown, but with both rectifiers65 and 66 shorted, trouble type signals would be delayed and alarm typesignals would not be delayed. The objection to this type circuitry isthat the purpose of the discernible alarm lamp 19 would be defeated bythe fact that it would also be energized when a delayed trouble typesignal appears.

It the alarm relay circuitry would be as shown, but with rectifier 66shorted, the system would operate as intended with the delayed troubletype signal and the instantaneous alarm type signal. This circuitryhowever has a hidden trouble possibility.

As is well known, all circuit connecting elements such as the ordinarywires used to interconnect most elements in the module 17 and tointerconnect the modules 17 and the various external elements of thesystem, such as the power source 28, have some measurable resistance. Inmost cases this resistance is so small as to be unimportant and isjustiably ignored in diagrams such as FIG. 3.

One such normally negligible distributed resistance 110 is depicted indashed lines superimposed on line 62 adjacent to terminal 61.

In a normal installation, the numerical value of resistance 110 is quitelow, and the effect that it would have on other units would benegligible even if rectifier 66 were shorted. There is, however, apossibility of the numerical value of resistance 110 becoming quite highunder a loose connection condition. It is under these conditions that anappreciable voltage would develop across this resistance as soon as asignal, either trouble or alarm, is initiated.

Under these conditions the voltage level at the line 62 side of alarmlamp 19 may be significantly different from that at bus bar 89. As, withdiode 66 shorted a current path exists through alarm lamp 19, resistance67, junction 64, diode 65, line 68, contacts 84 and 85, the line 87 andcoil 78 to bus bar 89 such a current can develop.

It is possible that the developed current could be of sufcient amplitudeto make the brilliance of the associated alarm lamp 19 enough to benoticeable and thereby confuse the attendant, and/ or reach the pick-uppoint of the relay 70 and thereby cause a chain reaction by an increasein the developed voltage across the resistance 110. The increase wouldbe due to the closed relay contacts of relay 70 and its associatedtrouble lamp 20.

In other words, under a trouble alarm condition, the voltage level atthe line 62 side of the trouble lamp 20 may be significantly differentfrom that at bus bar 89. As with diode 66 shorted, an initial currentpath exists from positive lines 57 and 93, through contacts 74 and 80 ofenergized relay 70, line 90, resistor 92, trouble lamp 20, line 62,resistor 110, to negative bus bar 89 such a voltage can develop atresistor 110.

Under a true alarm condition, the voltage level at the line 62 side oftrouble lamp 20 and alarm lamp 19 may be significantly different fromthat at bus bar 89 and to a greater degree than indicated for a troublealarm condition. As withwdiode 66 shorted, an initial current pathexists as vdescribed for a trouble alarm condition, and an additionalinitial current path exists from positive lines 57 and,56, throughclosed contacts 53 and 53 of energized relay 47, junction 64, resistor67, alarm lamp 19, line 62, resistor 110 to negative bus bar 89 such anincreased voltage can develop at resistor 110.

It is possible that the developed voltage at resistor 110 could be ofsufiicient amplitude to make the brilliance of an adjacent alarm lamp 19enough to be noticeable and thereby confuse the attendant, and possiblyreach the pickup point of an adjacent relay 70 and thereby cause a chainreaction by an additional increase of the developed Cil voltage acrossresistor 110. This additional increase would be due to the closed relaycontacts 74 and 80 of the additionally picked up relay 70 and itsassociated trouble lamp 20.

As, with diode 66 shorted, a dissipating current path, which causes abrilliance of an adjacent alarm lamp 19 and a possible pickup of itsassociated relay 70, exists from line 62 (positive side of developedvoltage) through adjacent alarm lamp 19, resistor 67, junction 64, diode65, line 68, line 86, closed contacts 84 and 85 of adjacent relay 69,line 87, adjacent relay coil 78 to bus bar 89k (negative side ofdeveloped voltage).

Although the possibility of this condition is remote, the blockingrectifier 66 is included to prevent this possibility and assure thereliability of the circuit and system.

Reliability of operation of the system may be doubled by using twoindividual modules 17 at the central station for each local station.This type of operation still only requires one pair of private lineconductors as ground is used as a third conductor but proper operationof the units is not dependent on ground conduction. For example, line 13may be normally maintained at a negative voltage below ground while line13 is maintained at a positive voltage above ground. In this case oneinput 42 of module 17 would be connected to line 13" and the other input41 connected to ground while the second module 17 of the pair would haveits input 41 connected to line 13 and its input 42 grounded.

For this double type of operation, the direct current voltage at thelocal station transmission conductors must of necessity be twice thevalue of a single unit type operation. The voltage must also be centertapped to ground. As with the single unit, the transmission conductorpolarities must be reversed by mechanism at the local station toinitiate an alarm type signal at the remote signal station.

Assuming that ground conduction and connections are normal, this type ofoperation would be able to transmit an alarm type signal on one of theunits even if the other unit already indicated a trouble type signal.This type of operation is lalso an asset for servicing, in that itprovides a better indication as to the nature and location of trouble.

Since this type of operation requires two individual component units perlocal location, the practical limit for a complete installation of thistype would be 50 local stations.

The preceding double module type of operation greatly increase thesecurity of a single module type, but for practical purposes, it wouldonly be used where a very high type of security would be required.

Referring again to FIG. 2, the optional alarm sub-system 5 will now bediscussed. The sub-system 5 including an additional alarm signalgenerator operated from a second alarm sensor 8 coupled as indicated bythe line 7 to the sensor 14. The second signal generator 9 is employedwhen a secondary indication of alarm condition is desired.

For example, it may be desirable in a bank to give a first alarm whenvan intruder enters the premises and a second alarm when the safe istampered with. The secondary alarm sensorfunctions only after theinitial alarm signal is sent. When this secondary system is employed theswitch 37 is opened. The generator 9 is normally closed circuited acrossthe switch 37 to allow unobstructed functioning of the generator 16.However, once the generator 16 is functioning to send the main alarmsignal the secondary alarm sensor 8 operates the secondary alarmgenerator 9 to cyclically open and reclose the circuit therethroughacross the switch 37.

This alternating secondary alarm signal functions to flash the alarmlamp 19 of FIGS. 1 and 3 to give added attention to the particularremote station. It does this thing without affecting the other aspectsof the circuit of the module 17.

lll

The circuit described above also provides reliability of operation.Conventional units pertaining to this type of remote signalling normallyprovide only a single relay with switch means for energizing audio andvisual signal units. The circuit as shown on FIG. 3 would be of thisconventional type if the following components were to be removed fromthe circuit: Relay coil 47 and its associated switch means, diodes 46,65, and `6:6, lines 56, 63, and 68, and alarm lamp 19, and resistor 67.

It is readily noticeable that a malfunction of a conventional singlerelay means would result in a malfunction of the unit. The malfunctioncould be electrical due to a contamination of the switch means, or itcould be mechanical which could prevent closure of the switch means.

The addition of diode 65, in the manner indicated on FIG. 3, provides asecond current path to the junction of lines 68 and 86 in the event of atrue alarm, and in this manner provides a greater reliability ofoperation than is available with the single relay type conventionalsystem.

In the event of a true alarm signal, a malfunction of the switch meansassociated with relay coil 47 of FIG. 3 would prevent energization ofthe alarm lamp 19, but the proper operation of the switch meansassociated with relay coil 50 would nevertheless cause the energizationof multiple contact relay 70, with subsequent energization of the audioalarm 24 and the trouble lamp 20 to indicate the source of the alarmsignal. A comparison of the lamp indication with the properly designatedmeter indication would nevertheless verify the alarm signal to be a truealarm signal.

In one practical embodiment of the invention a voltage source of twelvevolts, direct current, is employed for the remote signal unit, to resultin a small (two milliampere or less) current through the ammeter 43.Because of the small power loss the remote unit may employ a battery asits power source, thus making it independent of the public powerelectric sources and consequently not affected by failures of suchsources. Likewise, the central station may employ a similar twelve voltbattery pack as its source of power for the same reasons. Of course,other power sources such as the more conventional direct currentrectifiers may be employed, with or without a battery stand-by source.

As is now apparent the aforedescribed remote alarm system and circuit isboth easy and economical to install and operate and may even be operatedby a minimally trained or even an untrained attendant. The describedsystem and circuit provides for a plurality of alarm distinctions, whileat the same time providing protection against false actuation by atemporary short or open circuit.

Moreover, the system and circuit of the present invention are versatileand can be readily adapted and modified to different environments of useand differing alarm application.

For example, it will be readily apparent that other switch means such astransistors or electron tubes, may be ernployed in place of the relayswitches without departing from the spirit of the teaching of thepresent invention.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and, therefore, the aim in the appended claims isto cover all such changes and modifications as fall within the truespirit and scope of the invention.

I claim:

1. A remote alarm system comprising a plurality of remote stations eachhaving an alarm sensor, and an alarm signal generator actively coupledto `said sensor for activation thereby, said generator including asource of direct current;

a plurality of communication lines each of which is coupled, in anormally current carrying relationship, at one end to one of the alarmsignal generators of said plurality of remote stations, said sensor,

when activated, causing a variation in said normally carried current toconstitute a signal; and a central station coupled to the other end ofeach of said plurality of communication lines, said central stationincluding:

a direct current power supply; an audio alarm; a silencer for said audioalarm; and a plurality of modules coupled to said power supply, to saidaudio alarm, and to said silencer for separately and independentlyactuating said alarm and silencing said alarm, each of said modulesbeing coupled to the other end of a different one of said plurality ofcommunication lines and including:

at least one visual indicator; and switching means responsive to asignal on said coupled communication line to actuate said visualindicator and said audio alarm; whereby, in response to a signal on anyone of said plurality of communication lines, said audio alarm issounded and said visual indicator of the one of said plurality of saidmodules coupled to said any one of said remote stations is caused toindicate an alarm condition. 2. The remote alarm system as defined inclaim 1 in which:

said alarm signal generator of said each remote station produces adirect current signal of one polarity during normal operation and adirect current signal of the opposite polarity in response to activationby said alarm sensor. 3. The remote system as defined in claim 2 inwhich: said communication lines are of the two conductor telephone linetype. 4. The remote alarm system as defined in claim 3 in which:

said each of said modules is responsive to said signal of oppositepolarity on said two conductor communication lines to activate saidvisual indicator, and each of said modules includes a second visualindicator Which is activated in response to absence of said signal ofone polarity, and delay means for delaying the activation of said secondvisual indicator and for preventing the actuation of said second visualindicator should the absence of said signal of one polarity be onlytemporary. 5. The remote alarm system as defined in claim 4 in which:

each of said modules includes an ammeter actively coupled to the one ofsaid communication lines coupled to that module for indicating the ow ofcurrent therein. 6. The remote alarm system as defined in claim 5 inwhich:

said central station includes a source of direct current potential whichis coupled to each of said plurality of modules; said direct currentpotential of said source is electrically isolated by said plurality ofmodules from the currents from said communication lines; and each ofsaid modules includes switching means responsive to a reversal ofpolarity of said communication coupled thereto to connect the potentialfrom said source across said first lamp and to couple said potential tosaid audio alarm. 7. The remote alarm system yas defined in claim 2 inwhich each of said plurality of modules includes:

a pair of power input terminals for connection across a source of directcurrent voltage; a pair of input terminals for connection to one of saidplurality of communication lines; an audio output terminal forconnection to said audio alarm;

a silencer input terminal for connection to said silencer;

a signal detection circuit coupled across said input terminals forclosing a first switch means in the absence of a direct current of saidone polarity between said input terminals and for closing a secondswitch means in response to a direct current of said opposite polaritybetween said input terminals;

said at least one visual indicator is a first lamp which is connected inseries with said second switch means across said power input terminals;

a second lamp;

first means responsive optionally to said first switch means and to saidsecond switch means for connecting one of said power input terminals tosaid audio output terminal, to said second lamp, and to holding means,and for connecting said silencer input terminal tosilencer-signal-responsive second means, said second means responding tocause said connection of one of said power input terminals to said audiooutput terminal and to said holding means to be disconnected and tocause said connection between said second means and said silencer inputterminal to be transferred to a connection between said second means andsaid first switch means while maintaining said second lamp connectedbetween said power input terminals in such a manner as to diminish itsbrightness; and

said signal detection circuit includes delay means for delaying theactivation of said first switch means.

8. The remote alarm system as defined in claim 7 in which:

said first switch means is a normally open relay switch Whose relay coil(50) is connected in series with a first diode (45) across said pair ofcommunication line input terminals, said first diode being connected soas to prevent current ow therebetween when said direct currenttherethrough is in said one polarity and to allow current to flowtherethrough when said opposite polarity direct current is present;

said second switch means is a normally closed relay switch whose relaycoil (47) is connected in series with a second diode (46) across saidpair of cornmunication line input terminals, said second diode beingconnected so as to allow current fiow therethrough when said directcurrent between said signal input terminal is in said one polarity andfor preventing current flow when said signal is of the oppositepolarity;

said delay means is a capacitor (52) connected across said relay coil ofsaid normally closed relay;

each of said modules further includes an ammeter (43) connected to oneof said signal input terminals for determining the magnitude anddirection of current ow between said signal input terminals;

one of the switch terminals of said relay switch of said first switchmeans andl one of the switch terminals of said relay switch of saidsecond switch means being coupled to one of said power input terminals('58) and the other of the switch terminals of the relay switch of saidsecond switch Imeans being connected to a third diode (66) which isconnected in series in the said first lamp ,(19) in such a lmanner as toallow current to ow essentially only from the switch means to said firstlamp, said lamp also being connected to the other of said power inputterminals (61) so that said first lamp may light when the relay switchof said second switch means is closed;

said one power input terminal being for connecting to a positive inputfrom said power source and said other power input terminal being forconnecting to the negative input of said power source;

said means responsive to said first switch means includes a firstmultiple switch relay (70) having a first, second, third and fourthnormally open relay switches controlled by a single relay coil (78) anda second multiple switch relay (69) said first relay switch being inseries connection with said second lamp (20) and said series connectionbeing connected between said power input terminals, said second relayswitch having one switch terminal connected to the one power inputterminal (58) and the other connected to said audio alarm outputterminal (94), said fourth relay switch having one switch terminalconnected to the one power input terminal (58) and the other to acontrol coil (73) of said second multiple switch relay (69)( said secondmultiple switch relay coil controlling two relay switch blades (71 and72), one of which is part of a conventional normally open relay switchand the other of which is part of a make-before-break relay switchhaving two contact terminals (84, one of the switch terminals of theconventional relay switch of said second multiple switch relay beingconnected to the junction of the series connection of said first relayswitch and said second lamp and its other switch terminal beingconnected through a resistance (91) to said one power input terminal,the blade (72) of said make-before-break relay switch -being connectedto said other switch terminal of said fourth relay switch, said thirdrelay switch has one switch terminal connected to the one power inputterminal (58) and its other switch terminal connected to the other ofthe switch terminals of the Irelay switch of said first switch means,said makebefore-break relay switch having two contact terminals whichare normally connected but are open circuited when said switch blade(72) of said makebefore-break switch is activated whereby one of thosetwo contact terminals (85) is open circuited and the other (84) isconnected to said make-beforebreak switch blade, said one terminal beingconnected to one side of the control coil (7-8) of said first multipleswitch relay, the other side of that coil being connected to said otherpower input terminal (61) and said other switch terminal (84) of saidmake-before-break switch being connected to said other switch terminalof the relay switch of said first switch means; and

said modules further including a diode (65) connected lbetween the otherswitch terminals of the relay switches of said first and second fiowtherethrough only from said second to said first switch means.

9. The remote alarm system as defined in claim 7 including additionallyrectifier means in series with said second switch means and said firstlamp to permit current ow only in the direction of said alarm polarity.

10. The remote alarm system as defined in claim 1 wherein each of saidmodules includes at least one visual indicator; first switching meansresponsive to the signal on said coupled communication line to actuateand hold said visual indicator and said audio alarm;

second switching means responsive to said silencer to 15 16 for saidaudio alarm, said holding of an alarm con- References Cited dition isterminated, said audio alarm is silenced, UNITED STATES PATENTS and saidvisual indicator is retained, and g whereby, in response to arestoration of said normal 915075 3/1909 Clegler "6 17g-94 X 4currentcarrying relationship on said coupled com- 5 RALPH D, BLAKESLEE, PrimaryExaminer Imunication line, said visual signal and said switching meansare restored to normal Signal detecting U-S- C1' X-R- condition. 179-86;340-288, 326

